Third-grader Wilson Williams knows he'll never learn fractions: “Multiplication was hard enough,” he tells his pet hamster, Pip.

Worse, his parents have arranged for a math tutor. Just the idea of a tutor is embarrassing, but sympathetic Mrs. Tucker uses his love for hamsters to help him understand the math, and soon he’s quite clear about the difference between the Nice Numerator and the Dumb Denominator. At the same time, Pip becomes the basis for a successful science-fair project. Not only does Wilson have some academic success, he makes his little brother happy. Though only in kindergarten, Kipper has a science-fair project too. In the process of Kipper’s investigations, one of his favorite stuffed animals disappears. Big brother Wilson comes to the rescue. Most satisfying of all, he discovers that others—even his very best friend—are tutored, too. The short chapters have believable dialogue and plenty of reader appeal. In one, Wilson tries to teach his hamster to shake hands; in another, his friend Josh experiments with blowing up a pickle. Karas' scratchy grayscale drawings, one to a chapter, support the story. This sequel to *7 x 9 = Trouble* (2002) follows logically but also stands on its own.

Familiar school concerns, nicely resolved, make this another excellent selection for early chapter-book readers. *(Fiction. 7-10) *